Slope, Slope of Parallel Lines, and Slope of Perpendicular Lines

By: Paige Drummond

Melissa Le

Sydney Campo

To find slope-
The_slope.png
The slope intercept formula= Y=MX+B

Y=the Y corodinate (X,Y)- don't use
M= the slope of the line
X= the X cordinate-don't use
B= the Y-intercept (the point where the line crosses the Y-axis)

Point Slope Formula-
external image 11c4h3_1.gif


Slope=
external image slopes001.jpg



Slope of lines

Negative Slope
external image slope_negative.gif

Positive Slope-
external image Positive-slope.gif

Zero Slope-
external image detSlopeZero.gif
Undefined Slope-
external image typesslope3.gif

Slope of Parallel Lines- In a cooridinate plane two non-vertical lines are parallel if and only if they have the same slope.

Slope of Perpendicular Lines- In a coordinate plane two non-vertical lines are perpendicular if and only if the product of their slope is -1.


How to Calculate the Slope of Perpendicular Lines-
  • The product of the two slopes must be -1
  • They also must be opposite recipricals


Example-
external image reciprocal-4-over-3.png
Then, of course, you would make it negative for the opposite part.


Problem One-
By:Paige Drummond
Find the Line Perpendicular to this line.

external image alg_line1.gif


Answer-
First you must find the slope using the formula for finding slope.
The_slope.png
You can use any two points but for this problem we will use (-2,3) and (2,1).
The slope is negative one and a half.
Then to place it on the line pick a Y-intercept. The easiest on is always (0,0). Then you count over negative one and up two. Repeat this untill you have your line.

Practice Problem 2-
Melissa Le
Solve for y. Use the resulting equation to find the slope of the line.
9x – 2y = –18

Answer:step-by-step

Using the Addition Property, add –9x to both the sides.
(–9x) + 9x – 2y = (–9x) + (–18)
Simplify.
–2y = (–9x) – 18

Using the Multiplication Property, multiply both sides by –1/2.
external image image001.gif
Simplify.
external image image002.gif
Simplify the expression using the Distributive Property.
Here distribute –1/2.
external image image003.gif
The equation is in the slope–intercept form,
y = mx + b
Hence, the slope is 9/2.



online worksheet
http://www.mausmi.net/math-center/ws/Parallel%20and%20Perpendicular%20lines.pdf
http://www.themathpage.com/alg/slope-of-a-line.htm





Practice Problem: Find the slope of the line given in the graph below.
By: Sydney Campo

external image int_alg_tut15prob4a.gif
Answer:

external image int_alg_tut15ad4a.gif
Two sets of coordinates that we could use to solve this problem are (-3,0) and (0,5)
Using the formula for finding slope, y2- y1 , we subract 5-0= 5, and then 0--3= 3. The first equation gives us the answer to our "rise", and the second equation
x2- x1
gives us the answer to our "run".

Rise= 5
Run= 3
The slope = rise/run = 5/3